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Unformatted text preview: Quiz 1. Monday, January 28‘“, 2008 PHY 252 SOLUTION Name: 1. A wave has the form y(x,t) = Acos(61r X102[t+0.00291x]) in SI units.
a. In what direction is the wave traveling? (Explain clearly.) (3 points) [A 3CDL+ADCJ t+Ai) = Home).
"Flam, June amumeu‘b of ihe cosine musi‘ be Maud—
}.o. 617x102 C at + 0.002:ij :: candid willkeren‘tléte 1 (Ax __. doc. __ 1 o
n . 023 __ 2':— O ' __ __~ —————
6 “o 0 +00 lat) > c11 0.0029! ole: = — 344 Wis to 35545:.
ai—
‘, wave Es iraueuthj in “Ute. HOC direc‘éi'ou. b. Based on your knowledge of waves in media, what type of wave is this likely to be, and in
what medium is it likely traveling? Justify your answer. (2 points)
(Hint: What are the frequency and speed of the wave?) we have COMMQA the. speed) “U =2 “334148 TM freiueucj ILA obiaiuecj Camparl'ud our We 1'0 AmﬁwtiKac)
,'. Lg = 2713 = éﬂxlaz __=.> 5. z: 300 H2.
TLC» speed anal frezuent‘ ‘13 idpical. for salad Waves
‘  ' .., If U.
M at!“ ( Le, SPEECL. duct Mu.5lc . (Concert ﬂ L45 1? : ##OHZ) “Fl/Lula, slain. are. comsisl'emt Sauna! waves
7‘4 LMaJJ‘. ( on.“ Psalmties an}, at m be Supported)
EM mm are with! Guj— ‘SW ’V '5 C : 3x’ogm‘h' Quiz 1. Monday, January 28‘“, 2008 PHY 252 2. The relationship between air pressure P and air density p is P = [3 p, where [3’ is a constant. a. What are the dimensions of i3 ? (1 point)
B _ J9— : Fo Pee/area : Mass at acceleration
lo densii: are“ d deusfird
“7. __ M L‘T ‘ —2. * L1 1"— .ﬁ. cri WIDTS X 11 M/L3 CUcloeiL'ﬂ SZMQTEd3
b. The amplitude of a longitudinal sound wave in air, at position x and time t, can be written as a function x(x— vt) , where v is the speed of the wave. The equation describing the
propagation of sound waves in air is az_x _ ﬂ 6:2;
Biz 3x2
Use this information to derive an equation relating [3 and v. (3 points)
set P z ail—Wt 8% 3x. 32 31°
' _. = ._.. if) : ._ SUM—e —.. = i
From Chain rule 311: 8? Ba: 3P 3::
fee—appij chain rule 31);, = 3,9 ____ 31%
BEESL 3? P 5— 9 P‘“
SimilarLn] 32) = 333% 2 .v% saw 21° : —v
5‘; at. a at 3f 3
31%) .. v1 g2"
. é}? ‘ are
SuAsivl'lnt °"
3174 _ 7,1311 z 31"} = {3319‘ {3:331 *4
at; ‘— 3'31 31} 3’92
c. Given that the speed of sound in air at standard temperature and pressure is 334 m/s,
estimate the value of ﬂ for air. (1 point) 5 B=(33Ltm[5)1 :. 112 mo mtg“ "to 385.933. ~——% (1. Use this information to estimate the density of air at standard temperature and pressure.
(You will need to know/estimate the value of the “standard pressure”) (1 bonus point) i ai'MPLm % iiO‘gllJJM."~2~ (.YmﬁsLwukm P m sum‘z I . P {3 i.l'2.wo$' M15“ \1
A emit: copcan‘t answer is P = J: 2 lai'ha.
‘3 Lizua‘mls“ 5 ..
P ee‘iiuo nth5‘31; ...
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This note was uploaded on 05/11/2008 for the course PHY 252 taught by Professor Treacy during the Spring '08 term at ASU.
 Spring '08
 Treacy

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